Effective processing of carbon-containing waste material such as plastics, rubber and oil sludge has become a major environmental problem.
The incineration of waste material containing carbon, particularly plastics and rubber, leads to environmental pollution, whereas dumping of such unrecycled waste material in dump sites is not sustainable.
It is an object of this invention to provide a process and reactor for the pyrolysis of carbon-containing waste material. It is also an object of this invention to recover commercially valuable oil and amorphous carbon from waste materials containing carbon, such as oil sludge, plastics and rubber.
According to a first aspect of the invention there is provided a reactor for the pyrolysis of carbon-containing waste material, which includes:
a reactor vessel defining an air-tight reactor chamber, the reactor vessel having inlet means through which waste material can be introduced into the reactor chamber to be heat treated and outlet means for discharging heat treated material from the reactor chamber;a support tray that is disposed horizontally within the reactor chamber between the inlet means and the outlet means and that has a support surface for supporting a bed of the waste material;heating means for heating the bed of waste material on the support surface of the support tray, to a temperature sufficient to cause decomposition of the waste material into a gaseous product and a solid residue;a conveyor system for moving the bed of waste material along the support tray;vacuum means for forming a vacuum within the reactor chamber; andcooling means for cooling at least part of the reactor vessel thereby to provide for condensation of a portion of the gaseous product when it contacts the reactor vessel.
The cooling means may be in the form of a cooling jacket which surrounds at least part of the reactor vessel and in which a cooling medium, such as water, can flow, for cooling the reactor vessel.
The reactor vessel may have a first end wall structure at a first end of the vessel, a second end wall structure at a second end thereof and a cylindrical wall structure extending between said first and second ends.
The cylindrical wall structure of the reactor vessel may include an inner shell and an outer shell spaced therefrom, with the cooling jacket being defined between the inner and outer shells.
The first and second end wall structures may include spaced inner and outer shells, with additional cooling jackets being defined between the inner and outer shells.
The support tray may be disposed centrally within the reactor vessel, extending between the first and second ends of the reactor vessel.
The reactor vessel may include deflector means which is disposed above the support tray for deflecting the gaseous product towards sides of the reactor vessel, thereby to prevent droplets of condensed gaseous product from falling back onto the support tray.
The deflector means may be in the form of a deflector plate which is shaped to deflect the gaseous product towards sides of the reactor vessel.
The deflector plate may be spaced from and located above the support tray.
The heating means may be in the form of a furnace which is disposed externally of the reactor vessel and a heat exchanger in the form of a heating conduit for conveying air heated by the furnace, into the reactor vessel, the conduit extending for the length of the reactor vessel for heating the support tray and thereby the waste material supported thereon, via heat transfer to the support tray.
The conduit may follow a return path wherein the conduit extends from the furnace into the reactor vessel and substantially for the length of the support tray before returning to the furnace where reheating of the air takes place, in use.
The conveyor system may include a plurality of horizontally-spaced rake members which extend across the support surface of the support tray, the conveyor system being operable to displace the rake members along the support surface in a direction from the first end of the reactor vessel to the second end thereof, thereby to displace the particulate material along the support surface.
The rake members may be configured to alter the orientation of the waste material while displacing the waste material along the support tray, thereby to expose different surfaces of the waste material to heat so as to increase the rate of heat transfer to the waste material.
The reactor vessel may be adapted for processing hydrocarbon-containing waste material, the outlet means of the reactor vessel including an oil distillate opening through which condensed oil resulting from the pyrolysis of the waste material, can be discharged from the reactor vessel; and a solid residue outlet through which the solid residue can be discharged from the reactor vessel.
The reactor may include a solid residue screw-conveyor which has a first end located within the reactor vessel and a second end disposed externally of the reactor vessel, for conveying solid residue from the reactor vessel to a receiving bin.
The vacuum means may be in the form of a vacuum pump which is connected via a vacuum conduit, to the reactor vessel for reducing the air pressure within the reactor vessel to sub-atmospheric pressures.
The reactor may include a screw-conveyor for conveying waste material into the reactor vessel via its inlet means, the screw-conveyor extending into the reactor vessel for depositing particulate waste material onto the support tray near the first end of the vessel.
The invention extends to the reactor vessel as described and defined hereinabove.
According to a second aspect of the invention there is provided a process for the pyrolysis of carbon-containing waste material using the reactor in accordance with the first aspect of the invention, the process including:
introducing waste material into the reactor vessel of the reactor via the inlet means thereof;
heating the support tray and thereby the waste material to a temperature sufficient to cause decomposition of the waste material into a gaseous product and a solid residue;
displacing the waste material along the support tray from the inlet means to the outlet means of the reactor vessel;
cooling at least a portion of the reactor vessel thereby to allow for condensation of the gaseous product as it contacts said portion of the reactor vessel; and
collecting the resultant condensate and the solid residue.
The process may be adapted for use in processing hydrocarbon-containing waste material.
The process may include allowing the condensed oil distillate to run along a side of the reactor vessel within the reactor chamber, to a position within the reactor chamber where the oil distillate can be collected and discharged from the reactor vessel.
The process may include deflecting the gaseous product from a position above the support tray towards the side of the reactor vessel thereby to prevent droplets of condensed oil distillate from falling back onto the support tray.